The project main goals are to solve the problem of high organic load effluents in the marinated herring industries by investigating environmentally friendly and cost effective technological solutions and to characterize and valorise the molecules obtained from the organic fractions recovered. The intermediate objectives are delineated in 4 work packages

Ceramic membranes and electrochemistry separation technologies, either alone or in combination, were tested on different process water streams generated during the production of marinated herring. Electrochemical flocculation (EF) and ultrafiltration (UF) using ceramic membranes (0.04 µm SiC membranes) in a crossflow setup, were applied on all types of process waters generated during production of marinated herring – refrigerated sea water (RSW), storage water (SW), processing water (PW), different salt brines (SB), and the final ripening brines (TSp, TSa, SC, VC). EF was used in a pre-filtration step and compared to polypropylene filtratation (PF) The tests were conducted batch wise on site at the herring producers on 100-1000L freshly collected process waters. The impact of consecutive EF-UF and PF-UF treatments were analysed, and the latter combination gave retentions of up to 42% COD (chemical oxygen demand), more than 95% TSS (total suspended solids), more than 85% iron, up to 44% nitrogen, 100% fatty acids and more than 80% protein using the final ripening brines (TSp, TSa, SC, VC). For EF-UF treatment of SB effluents, retention of 70% COD and 79% protein was obtained, whereas UF alone only retained 67% COD and 36% protein. Thus ceramic UF has potential as a separation technology for the marinated herring process waters, although further investigations of pre-treatment technologies are needed to obtain a better flux

The project provided evidence for:

Applicability of the tested technology alone or in combination for separation and recovery of organic material from herring industry processing waters

Characterization of Fractions

The aim of WP2 was to quantitatively and qualitatively characterize the composition of the crude process waters and the fractions obtained after separation e.g. with UF. Analyses included: protein, fatty acids, free amino acids, dry matter, COD/BOD and trace elements. Waters characterized included refrigerated sea water (RSW), storage water (SW), processing water (PW), salt brines (SB), and in the final ripening brine (TSp, TSa, SC, VC). Results showed that large amounts of biomass are currently lost per tonne of processed herring; in the first steps (the boat step to barrel step) this loss represents approximately 10 kg proteins and 4 kg of fatty acids and in the second marination steps (i.e. from barrel to final glass jar) up to 110 kg protein and 40 kg fatty acids are lost. All in all, 7 m3 of water is consumed throughout the process per tonne of final product. An interesting notification in this project part was that the composition of the waters is highly dynamic, and depending on the time during which herring is incubated in the different waters; more biomolecules leach out. This leaching was also affected by the degree of tissue disintegration and the level of salt in the waters. As stated in the previous section, separation trials using UF resulted in outlet fractions containing low amounts of fat and proteins and could represent an alternative for recovery of biomass from process water, provided that an appropriate pre-treatment is used. The fractions recovered were rich in protein and fat and this technology could thus represent a new way of collecting fish biomass for further valorisation.